Magnetic field magnitude distribution on a cross section of a toroidal flux rope. The generating toroid has the aspect ratio 2.5, and the generalization of the Lundquist field (9)–(11) was used for the field construction. Its free parameters were M = 1, d₀ = 0, d₁ = 0, e₁ = 1. The closed lines are cross sections of magnetic surfaces that have (non-ideal) toroidal shapes and on which helical magnetic field lines lie.